1. Field of the Invention
The present invention relates to a line filter to be inserted into the input portion or the output portion of a power source (a single-phase power source).
2. Description of the Related Art
FIGS. 1 and 2 respectively illustrate a conventional line filter disclosed in, for example, "Noise Technology for Electronic Circuit", p.p 116, edited by Yamazaki and published by Ohm Corp. FIG. 1 illustrates an equivalent circuit in an electrical view point and FIG. 2 illustrates an example of the structure of the conventional line filter. FIG. 1 illustrates a combination of a filter reactor 15 and a capacitor 16 for bypassing a noise current. FIG. 2 illustrates the reactor 15 shown in FIG. 1 and arranged in such a manner that two coils 17 and 18 are wound around a core 19, the two coils 17 and 18 being wound symmetrically with respect to the center of the core 19.
In the reactor 15 constituted as described above, although a signal common to the electric circuit does not affect the polarities of the two coils wound as described above, the noise of the same phase is inhibited. Noise, which has passed through the reactor coils 17 and 18 after inputted from input terminals K and L, is bypassed by the capacitor 16 so that the generation of the noise in the load side terminals k and l is prevented. In this case, the capacitor 16 is connected to the reactor 15 via lead wires.
Since the conventional line filter has been constituted as described above, an inductance is undesirably generated due to the presence of the lead wires which are used to connect the capacitor. Therefore, the capacitor may not work as desired in a high frequency range. What is even worse, since the lead wire for establishing the connection of the external capacitor must be shortened, the connection cannot be easily completed. Another problem arises in that the capacitor must have excellent high frequency characteristics.